A trailer is an unpowered wheeled vehicle that is used for hauling cargo. The surface upon which the cargo rests is most commonly known as a bed, but is also known as a deck or a platform. Trailers having an uncovered flat bed are used to transport motorcycles, lawn tractors, all terrain vehicles, watercraft, and other personal cargo. Flat bed trailers typically contain tongues with couplers that attach to a trailer hitch mounted on the back end of an automobile or truck.
Flat bed trailers typically include a suspension system to dampen the movement of the bed as the wheels pass over uneven surfaces. Suspension systems typically include coil springs, shock absorbers, or struts that are mounted between the components that support the wheels and the bed. Suspension systems containing airbags have also been disclosed. For example, De Roshia, U.S. Pat. No. 3,102,738, Sep. 3, 1963; Gladish, U.S. Pat. No. 4,335,901, Jun. 22, 1982; Smith et al., U.S. Pat. No. 4,934,733, Jun. 19, 1990; Smith, U.S. Pat. No. 5,275,430, Jan. 4, 1994; Nowell et al., U.S. Pat. No. 5,560,639, Oct. 1, 1996; Overby et al., U.S. Pat. No. 5,951,032, Sep. 14, 1999; Wayrynen, U.S. Pat. No. 7,281,728, Oct. 16, 2007; Sherwood, U.S. Pat. No. 7,537,219, May 26, 2009; and Fankhauser et al., U.S. Pat. Appln. Publn. No. 2010/0289250, Nov. 18, 2010, disclose trailers having air bag suspension systems.
Flat bed trailers are relatively bulky and take up considerable storage space when not in use, when on display at retail stores, and when shipped from the point of manufacture to the point of sale. To reduce the storage space, trailers having folding beds have been disclosed. For example, Burris, U.S. Pat. No. 4,239,258, Dec. 16, 1980; Spainhower, U.S. Pat. No. 7,540,528, Jun. 2, 2009; and Fahrbach, U.S. Pat. No. 7,891,697, Feb. 22, 2011, disclose folding flat bed trailers. The Spainhower trailer has a bed with two folding sections and has a tongue connected to the rear section. The Burris and Fahrbach trailers have beds with three folding sections and have a tongue connected to the middle section.
The bed of a flat bed trailer must be high enough above the ground to provide adequate clearance when the trailer is towed. Light weight cargo can be lifted up manually from the ground onto the bed, but other means must be used to load heavy wheeled cargo such as motorcycles, lawn tractors, and all terrain vehicles. A first method for loading is to employ a powered lifting device such as a fork lift truck. However, fork lift trucks are rarely available for personal use. A second method is to load and unload the trailer from an elevated platform such as a loading dock. Again, elevated platforms are rarely available for personal use. A third method for loading is to use a ramp consisting of long wood or metal planks between the bed and the ground. Ramps are prone to loss and must be secured onto the trailer during transport.
A fourth method for loading a trailer is to include a folding ramp as part of the bed of the trailer. For example, trailers with folding ramps that are part of the bed are disclosed in Law et al., U.S. Pat. No. 4,514,132, Apr. 30, 1985; and Thedford et al, U.S. Pat. No. 7,909,355, Mar. 22, 2011. The folding ramp is lowered to the ground for loading or unloading and is raised during transport.
A fifth method for loading a trailer is to lower and tilt the entire bed. For example, lowering and tilting trailers with airbag suspensions are disclosed by Nowell et al. and Fankhauser et al. as previously cited. Nowell et al. disclose a four-wheeled trailer having an airbag suspension on the rear pair of wheels that, when the airbags are deflated, allows the entire bed of the trailer to lower and tilt toward the rear. The entire bed thus forms a ramp upon which the cargo can be loaded. Fankhauser et al. disclose a two-wheeled trailer having an airbag suspension that, when the airbags are deflated, allows the entire bed of the trailer to lower.
Notwithstanding the many trailers that have been disclosed, there continues to be a demand for an improved folding bed trailer that tilts and lowers with a compact airbag suspension.